This invention relates to an arrangement for supplying energy to a load dependent upon a binary signal comprising a low-frequency component and a strong high-frequency component having a predetermined frequency which, load has a low-pass frequency characteristic. In a first energy supply state the arrangement is arranged to supply energy to the load by means of an electric quantity with a specific polarity, in a second energy supply state it supplies energy to the load by means of an electric quantity with a polarity opposite to the specific polarity and, in a third energy supply state it interrupts the energy supply to the load. The arrangement comprises a control circuit for alternately causing the arrangement to adopt different energy supply states according to a switching pattern determined by the binary signal.
The invention likewise relates to a drive system comprising such an arrangement disposed to energize an exciter coil of a motor of the drive system.
The invention further relates to a sound reproduction system comprising the above arrangement adapted to energize an electroacoustic converter.
A drive system of the type mentioned above is known, for example, from DE-OS 25 58 571.
In the prior art drive system a dc motor is supplied with energy by means of a so-called H-bridge in which, in a first energy supply state, the motor is energized by a dc voltage source through two diagonally opposite switches in the H-bridge. In the second energy supply state the motor is energized by the same dc voltage source through two different diagonally opposite switches of the H-bridge. In the third energy supply state the motor is short-circuited by means of two switches of the H-bridge. The control circuit receives two pulse-width modulated binary signals which are each other's inverse value apart from a mutual phase shift. The phase shift is such that the ascending edge of one binary signal coincides with the descending edge of the other binary signal. The switch control signals for causing the H-bridge to adopt one of the three energy supply states are derived from these two binary signals. In the case where the two binary signals exhibit different signal values, the H-bridge is brought to the first or the second energy supply state depending on the sign of the difference between these signals. If the signal values of the two binary signals are equal, the H-bridge is made to adopt the third energy supply state in which the supply is interrupted. In this manner the motor is energized with a current largely determined by the dc voltage component of the binary signal, so that the power dissipation produced in the motor and switches by the high-frequency component of the binary signal is reduced considerably relative to an energy supply with pulse-width modulated operating voltages, while no use is made of the third energy supply state. The drawback of the prior art arrangement is, however, that deriving the control signals which denote this third energy supply state is extremely complex.